Method of and apparatus for producing a wide metal strip by rolling



Oct. 26, 1965 T. SENDZIMIR 3,213,661

METHOD OF AND APPARATUS FOR PRODUCING A WIDE METAL STRIP BY ROLLING Filed Nov. 2. 1961 8 Sheets-Sheet 1 INVENTOR TADEUSZ SENDZ/M/R Oct. 26, 1965 sENDZlMlR 3,213,661

METHOD OF AND APPARATUS'FOR PRODUCING A WIDE METAL STRIP BY ROLLING Filed Nov. 2. 1961 8 Sheets-Sheet 2 INVENTOR THDE U 52. SENDZ/M/R Oct. 26, 1965 T. SENDZIMIR METHOD OF AND APPARATUS FOR PRODUCING A WIDE Filed NOV. 2, 1961 METAL STRIP BY ROLLING 8 Sheets-Sheet 3 INVENTOR Oct. 26, 1965 'r. SENDZIMIR METHOD OF AND APPARATUS FOR PRODUCING A WIDE METAL STRIP BY ROLLING Filed NOV. 2, 1961 8 Sheets-Sheet 4 INVENIOR THDfl/SZ SENDZ/MIR Oct. 26, 1965 'r. SENDZIMIR 3,213,661

METHOD OF AND APPARATUS FOR PRODUCING A WIDE METAL STRIP BY ROLLING Filed Nov. 2. 1961 8 Sheets-Sheet 5 INVENTOR THDEUSZ SENDZIMIR Oct. 26, 1965 T. SENDZIMIR 3,213,661

METHOD OF AND APPARATUS FOR PRODUCING A WIDE METAL STRIP BY ROLLING Filed Nov. 2, 1961 8 SheetsSheet 6 RNGULHR POSITION 0F WORK ROLLS PRL'CEDING FOLLOW/N6 ROLL TOUC'HEZS 5MB ROLL TOUCHLS SL/JB INVENTOR THDEUSZ 5ENDZ/MIR Oct. 26, 1965 'r. SENDZIMIR 3,213,661

METHOD OF AND APPARATUS FOR PRODUCING A WIDE METAL STRIP BY ROLLING Filed Nov. 2. 1961 8 Sheets-Sheet 7 INVENTOR 77905052 SENDZ/M/R Oct. 26, 1965 T. SENDZIMIR 3,213,661

METHOD OF AND APPARAT FOR PRODUCING A WIDE METAL STRI Y ROLLING Filed Nov. 2 1961 8 Sheets-Sheet 8 INVENTOR United States Patent 3,213,661 METHOD OF AND APPARATUS FOR PRODUCING A WIDE METAL STREP BY ROLLHNG Tadeusz Sendzimir, R0. Box 1350, Waterbury, Conn. Filed Nov. 2, 1961, Ser. No. 149,642 11 Claims. (Cl. 72190) The present invention relates to the method of and apparatus for producing wide strips of metal or other substances by plastic deformation in the hot or cold state, and particularly to the reduction from so-called slab form to strip form. The term slab, when applied to steel, means a semi-finished product after reduction from the ingot on a so-called blooming or slabbing mill or to a product produced directly by casting. A slab is usually a piece of material of rectangular cross-section whose width is several times its thickness and whose length varies from a few to several feet. The slab may also be of continuous length if it is produced by continuous casting. In low carbon steel a typical slab would have a cross-section of, say, 7" x 50 and would weigh approximately 20 tons. This slab would serve as a base material for the production of a strip which is also about 50 wide but only 0.080" thick. Such a strip is usually collected in coil form.

The principal objects of this invention are the provisions for improvements which effect the operation of rolling instrumentalities such as the ones used for the reduction of the type described in the preceding paragraph, particularly the method of feeding the workpiece into the roll bite of said rolling instrumentality so that a great portion of the rearward force exerted on the workpiece by the planetary work rolls is absorbed by an element whose embodiment is hereafter described.

Another object is to provide a cyclic mill with a distance between the feeding means and the cyclic reducing instrumentality long enough to accommodate second stage heating means for the workpiece and thus reduce scale and heat losses.

A further object is to provide a planetary mill capable of operating in a direction opposite to the movement of the workpiece for the purpose of (l) Scarfing the slab as an integral part of the rolling operation, and

(2) Reducing the size and, therefore, the cost of the mill,

for a given thickness of slab.

Still another object is to roll a wide strip from a single narrow slab with the added advantage of producing various widths of strip from a single width of slab. This eliminates the necessity of a longitudinal weld between two or more strips.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangements of parts which are adapted to eflect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic, partially cut-away side elevational view of a cyclic reducing mill of the planetary yp FIG. 2 is a diagrammatic plan view of the mill shown in FIG. 1 with the upper planetary assembly and the upper feed roll omitted;

FIG. 3 is a side elevational view of a planetary mill according to this invention, looking from the slab entry side thereof;

FIG. 4 is a diagrammatic horizontal cross-sectional view of the mill taken along line 44 of FIG. 3;

FIG. 5 is a plan View of the force-absorbing element according to one embodiment of the invention;

FIG. 6 is a partial sectional view of the force-absorbing element taken along line 66 of FIG. 5;

FIG. 7 is a diagrammatic side elevational view of a mill according to the invention, showing the movement of the elements in reverse rolling;

FIG. 8 is a side elevational view of a mill according to the invention showing a difierent type of feeding mechanism;

FIG. 9 is a sectional view of the feeding mechanism of FIG. 8 showing the driven shaft and adjusting mechanism therefor;

FIG. 10 is a horizontal sectional view taken along line 1tl10 of FIG. 9;

FIG. 11 is a graph illustrating the fluctuation of the total backward thrust exerted on the slab; and

FIG. 12 is another embodiment of the contacting surface of the force-absorbing element shown in FIG. 5.

The present invention is applicable when the rolling instrumentality is of the cyclic type in which, generally speaking, a heavy single pass reduction is obtained. For instance, the plastic reduction from slab to strip of low carbon steel of the dimensions shown in the first paragraph could be produced in a single pass in the cyclic mill.

In contradistinction to conventional mills where the rolls turn around fixed axes and propel the material forward as the reduce it, one characteristic feature of a cyclic type of rolling mill is that each work roll or each pair of cooperating work rolls also has a translation movement either in the direction of rolling or in the opposite direction. The translational movement is at a speed substantially greater than the forward progress of the workpiece, and the workpiece must be fed into the roll bite by external means.

One example of such a cyclic rolling instrumentality is described in US. Patent No. 2,878,697, which discloses a reciprocal rolling mill conceived by F. R. Krause. This type of mill is equipped with a pair of heavy pinch rolls capable of feeding the workpiece to and through the mill at a controllable velocity independent of the translation, direction of rotation and speed of the work rolls.

Another example of such a cyclic rolling instrumentality is the planetary mill described in US. Patent No. 2,811,060. The diagram of forces presented in FIG. 3 of the latter patent shows the variation of the feeding force necessary in connection with the relation of the position of the work rolls and it will be readily seen that there are never less than one or more than two pairs of feed rolls simultaneously in contact with the workpiece. This force may vary, from a peak force where each work roll first contacts the slab, to a minimum force where the reduction is nearly completed, by as much as 5:1 or more. The feeding instrumentality, which in this case is one or more pairs of feed rolls, while making a certain reduction of the workpiece in order to produce the friction conditions for the necessary feeding force, must also take those peak forces. Those forces may reach as much as one-third or more of the roll separating force of the work rolls. Therefore, this calls for a very powerful and heavy mechanism, and even so, in view of the sharp fluctuations of the feeding force requirements, the spindles of such rolls are not subjected to a continuous load, but to cyclic load fluctuations in synchronism with the variation of the feeding force requirements. Due to the great force that the feeding apparatus exerts on the slab, in order toovercome the rearward directed thrust acting on the slab and to achieve satisfactory feeding, such apparatus must be placed as close as possible to the zone of plastic reduction in order to avoid bending.or buckling of the slab between the Zone and the feeding apparatus, because the slab in this sector is subjected to a substantial compression. Such compression may produce a loop or buckle of the workpiece at the mill entry, if a certain limit of the compressive force is exceeded, or if the unsupported length of the slab is too great. Another peculiarity inherent to the above-mentioned cyclic rolling apparatus, is that there is relatively little side spreading of the workpiece so that the width of the rolled strip is substantially equal to and limited to the width of the slab which is being fed into the mill.

Referring now to the drawings, a straight planetary rolling mill, such as the one referred to in the preceding paragraph, is shown in FIGS. 1 and 2. In such a mill a slab or workpiece is introduced into the roll bite B, by a pair of feed rolls 11, where the workpiece is subjected to the intermittent action of work rolls 12, which roll over the surface of the workpiece 10, effecting the plastic deformation thereof. Each work roll takes a small individual reduction, but the sum of the successive individual reductions produces an extremely large single pass reduction so that workpiece 10 leaves the mill in the form of-a thin strip 13. The work rolls 12 are journaled at their ends in rings or cages 14 which are placed at both ends of the back-up rolls 15 which in turn are journaled in eccentric chocks 38 located in the housing and around which the work rolls 12 are arranged and rotate in a planetary fashion. The feed rolls 11 and the planetary work rolls 12 are driven by suitable means not shown which supply the necessary torque through the couplings 16 and 17 to feed roll shafts 18 and planetary back-up roll shafts 19 respectively. The feed rolls 11 are located as close as possible to the planetary assemblies so as to minimize the length of the workpiece affected by the rearward directed thrust exerted upon the workpiece and which must be absorbed by the feeding instrumentality.

In the present inventionapplicant has devised a method of relieving the feeding instrumentality of a part of the force which is exerted on the workpiece in order to meet and overcome the backward directed thrust and achieve a positive feedingspeed of the workpiece into the roll bite. The present invention also avoids other disadvantageous factors inherent in the conventional cyclic rolling method described in the preceding portion of the present application, including inaccessibility and lack of space for certain very necessary elements.

This method consists of not feeding the workpiece straight into the mill as described in the previously mentioned Patent No. 2,811,060, but at a considerable angle, such as between 30 and 70 and even more.

It is known in the art to feed two slabs simultaneously into the roll bite of a planetary mill at equal but symmetrically opposite angles to the direction of rolling. Patent No. 2,787,046 to J. B. Wagstatf discloses a method of producing a wide metal strip by longitudinal welding of edges of two slabs, which converge into the bite of a planetary mill. Wagstaff has observed that two slabs so converging will weld along their contacting edges during the rolling operation. Since the position of the slabs in Wagstaff are symmetrical in respect of the mill, the side thrusts of the two slabs cancel each other since each slab exerts a heavy side thrust against the other. These forces are helpful in assuring a longitudinal weld during the plastic reduction of the slabs. The Wagstatf method, therefore, aims solely toward increasing the width by the physical unification of two slabs into a common strip.

In contradistinction with the above-mentioned Wagstatf method, the present invention is directed to reducing the forces which. are acting on the feeding instrumentality during rolling operations, by feeding only one workpiece angularly into the roll bite and taking advantage of the unbalanced side thrust and of the friction conditions existing in the contact area between the outer edge of the workpiece and the thrust-absorbing element in the form of a side guide 21 whose location and exemplary embodiment is illustrated in FIGS. 4 and 5. The rearward reaction of the work roll pressure is shown as vector OY in FIG. 4. The feeding force required to overcome the work roll pressure is not as shown in a previously menti-oned U.S. Patent No. 2,811,060, but is a vector quantity OX directed at an angle on from the direction of rolling. In this manner, only one component, vector OX, is directed axially to the workpiece and this component of the force is the only one that must be met by the feeding rolls 11. The other component, vector OZ, is directed sideways and perpendicular to the direction of feed of the workpiece, and according to the present invention, this component is automatically absorbed by a thrustabsorbing stationary or vibrating side guide 21 against which the outer edge of workpiece 10 abuts. The bigger the angle a, the bigger the portion of the rearward force exerted by the work rolls which is absorbed by side guide 21 and the smaller the portion which has to be overcome by the feeding rolls 11.

According to the invention, side guide 21 may be of any suitable construction, provided it is adequately strong to take up heavy thrust pressures and rigidly anchored to the mill housing and it is preferably faced with a wear resistant lining at the surface which contacts the edge of the slab 10. Whenever slab 10 is rolled in a hot condition, it is preferable to provide a guide with a heat insulating layer between the heat and wear resistant face lining and the structure of the guide itself, to prevent withdrawal of heat from the edge of the slab by contact with the guide. Such a heat insulating layer suitable for the purpose is described in US. Patent 2,811,060, where it is shown used as an element of a feeding instrumentality. It preferably consists of a multicellular structure 22 which is interposed between guide 21 and the slab contacting surface and which serves as a heat insulator to prevent dissipation of the heat absorbed by the contacting surface of the red hot slab while retaining the necessary mechanical strength. The slab contacting surface of the side guide, which may even be of concave section if round edged slabs are rolled, is faced with a heat resisting material 23, such as Stellite or the like, in order to minimize wear. The surface of heat resisting material 23 may have the configuration shown in FIG. 5 or an alternate configuration such as the saw tooth configuration shown in FIG. 12.

During the rolling operations the workpiece abuts the contacting surface of the side guide 21 and the friction between it and the workpiece helps to achieve a selflocking or near self-locking condition of the workpiece during the peak of the thrust force, vector OY. During the portion of each cycle when the thrust force is lowest, the feeding rolls 11 can feed workpiece 10, the required step, while encountering only a small resistance, which is many times smaller than straight rolling in planetary mills. This self-locking or near self-locking condition in angular rolling constitutes a further improvement in that the workpiece is not fed into the roll bite at a uniform speed, but in fast intermittent strokes, one for each pair of passing work rolls 12. Such intermittent movement will be synchronized and in phase with the action of the work rolls entering the roll bite in the reduction zone, so that the forward stroke of the slab is effected in the precise time period when the rearward force exerted by the work rolls against the workpiece is at its minimum.

The intermittent movement of the workpiece entering the roll bite is inherent in planetary mills, because the back thrust which the work rolls exert against the workpiece is cyclic and not uniform and reaches its maximum shortly after a pair of work rolls first contacts the workpiece and reaches its minimum just before the next pair of the Work rolls makes contact in turn. The fluctuation of the feeding force is shown in FIGURE 11, where the rearwardly directed thrust exerted by the Work roll against the workpiece is graphically plotted. In FIG. 11 the dotted line represents the fluctuation in magnitude of the rearward thrust forces exerted individually by each pair of work rolls, in relation to their angular position in the roll bite. The peak of the curves corresponds to the point P, where the work roll first establishes full contact with the workpiece, and from there, the magnitude of the force gradually decreases, as the work roll progresses through the roll bite, until it reaches a negative value just before each roll completes the reduction of the workpiece at the point B. In an exemplary embodiment, such as shown in FIG. 1, the following roll contacts the workpiece before the preceding roll has reached the point E and has lost contact with said workpiece. The solid curve represents the summation of overlapping dotted curves for adjacent work rolls. This, therefore, represents the total force that must be applied by the feed rolls.

According to a further improvement of the present invention the condition of intermittent feeding is facilitated by providing the guide itself with a vibratory movement in synchronism with the passage of the work rolls, pair by pair, using any conventional vibrating means, such as mechanical cams or eccentrics, hydraulic vibrators, electromagnetic vibrators fed from a variable frequency generator in order to synchronize it with work rolls 12, or even using the principle of mass disequilibrium such as is known in concrete shakers, etc.

Therefore, the difference between a stationary and vibrating guide is a question of degree. A slab abutting a stationary guide will be released during each cycle at the point where the back pressure by the work rolls is at its lowest, so the feed rolls can overcome the remaining resistance. With a vibrating guide, the crest of the back pressure is actually met by the forward movement of the guide. 'While at the ebb of the back pressure, the guide recedes and the feed rolls push the slab forward against virtually no frictional resistance.

Another advantage of vibrating guide, whether in synchronism with the work roll contact or not, is that it reduces the time the guide contacts the edge of the slab and therefore, reduces the cooling effect, which is detrimental to the edge.

In most cases, where it is preferable to still further reduce the feeding force, I prefer to use a mechanism which produces not only a linear vibration but a circular or rectangular movement, or even superposed vibrations in two directions including a component in the direction of the movement of the slab during the portion of the cycle when the guide 21 is pushed towards the edge of the slab.

An exemplary embodiment of the vibrating guide with a circular motion and of its mechanism is illustrated in FIGS. 5 and 6. The side guide 21 is mounted on two or more eccentrics 24, the simultaneous rotation of these eccentrics is accomplished by a combination of gears 25 which are keyed to shafts 26 on which the eccentrics are mounted. These shafts are driven by gears 27 which are keyed to a common driving shaft 28. The eccentrics and the driving shaft are rotatably mounted in a casing 29 by suitable means, the casing forming an oil bath for the rotating members. The entire mechanism of the vibrating side guide is rigidly anchored to the mill housing. The temperature of the side guide assembly is controlled either by circulating coolant through the connection 30, provided for such purpose in the side guide body, or by external water spray.

It should be understood that the preceding paragraph describes only one embodiment of a mechanism which would provide the side guide with a circular or straight vibratory movement and in no way excludes the possibility of using other mechanical, hydraulic, electrical or centrifugal systems, in order to obtain similar results. The synchronization of the side guide vibrating motion, and the adjusting means for bringing it into the best phase relationship with the position of the work rolls as explained heretofore, can be accomplished not only by varying the vibratory frequency of the side guide, but identical results can be obtained if the vibratory frequency of the side guide remains constant and the speed of the planetary mill is adjusted so that the conditions of in phase synchronism are satisfied, for instance, where the guide is vibrated by standard 60-cycle alternatlng current.

In using such a side guide, whether stationary or vibrating, certain difficulties have arisen due to the fact that with angular rolling it was impossible to produce a straight strip, which had a tendency to curve violently in the direction away from the angle of feed.

A careful analysis of conditions of plastic deformation applying on the outward as compared with the inward angles at the point where the undeformed slab enters into the zone of deformation and again compared with conditions applying in case of a straight rolling cyclic mill have led applicant to provide a supplementary side guide 31 extending beyond the contact area of the principal side guide 21 in the direction of rolling and capable of exerting lateral thrust against the edge of the slab at the outward corner and especially beyond the corner while at least the slab is in the first half of the reduction zone. I found that the inclination of the added support which is generally in the direction of rolling is very critical but that after I have adjusted its shape and inclination to produce a straight slab, the mill conditions remained stable. I have also found that the provision of such supplementary guide has enabled me to produce strips with the corresponding edge substantially free from cracks. For these reasons the side guide 21 is provided with an extension 31 as shown in FIGS. 5 and 6. The extension 31 is mounted at the end of the side guide contacting area, at such angle that it follows the departure from straight line of the slab being reduced in the roll bite, serving as a rigid support of the workpiece during the plastic deformation of the same. As explained, the angular position of the guide extension, and, therefore, the pressure that this complementary guide exerts against the side of the slab, is critical for production of a straight strip and, therefore, I prefer to make it adjustable, for instance, by means of screw 32 which may be adjusted to cause a spacer 33 to separate supplementary side guide 31 which is pivotally mounted to side guide 21 by a greater or lesser amount, thereby adjusting the angle. The adjustable side extension can be anchored in the main side guide body 21 and, therefore, subjected to the same circular or vibratory movement as the guide itself. Or it may be located independently from the guide end and remain at rest and not participate in the movement of the side guide 21. Because the side extension 31 extends into the roll bite, it must have such a shape as not to interfere with the path of the passing work rolls. The contacting surface of the guide extension is also protected by a facing of heat resistant material 23, such as Stellite and the like. When the best relative angular setting of the adjustable side extension 31 has been found by experience on a given planetary mill and for a given workpiece and material, its position can be then fixed and replacement of the side guide can be made so that the main body 21 and the extension 31 are in one piece as shown in FIG. 4 which reduces maintenance costs.

The area of highest concentration of the pressure exerted by said side guide extension 31 against the edge where the slab is being reduced to a strip by the Workrolls is quite critical. By making the face of said guide extension 31 slightly convex, I found that the angular 7 V adjustment of said guide permits to easily influence the position of the area of highest pressure concentration in relation to the beginning of the roll bite. In this manner, I am able to counteract the effects of asymmetric slab support in the deformation area by adding support and increasing onpurpose the effective pressure in the edge zone at the slab corner forming an obtuse angle with the direction of rolling.

The substantial reduction of the feeding force needed in theplanetary rolling process accordingto the present application, opens another possibility of profound advantage to the carrying out of said process. This concerns a more advantageous heat balance of the system. As mentioned above, in the normal straightline planetary rolling mills such as are exemplified in FIG. 2 of US. Patent No. 2,710,550, the feeding force which is necessary to overcome the backward thrust of the work rolls is of such magnitude that the feed rolls have to be disposed as close as possible to the planetary reducing roll so as to shorten as much as possible the length of the slab which is under compression between the two rolling instrumentalities. Otherwise a buckling would occur. Buckling can be partially corrected by suitably disposed top and bottom guides but that introduces heavy friction between the slab and the guides, which again makes rolling very diflic-ult. Let us consider hot rolling of steel slabs, say for example, 4" thick x 40" wide, to strip 40" wide x 0.080 thick. Such a slab will have to be continuously heated, for instance, in a tunnel furnace in line with the mill, to such temperature that on entry into planetary mill, the slab has the required hot rolling temperature. This will depend on the analysis of thesteel and on the grain size and physical properties of the hot rolled steel required, and usually lie between 850 and 1000 or even 1100 C. Such a slab would be fed into the mill at a speed between 5 and 8 f.p.m., for example, and, therefore, there are several minutes passing between the time when the strip leaves the furnace and when it enters the planetary mill bite. During this time the slab, which has been descaled as it leaves the furnace, such as by high pressure water jets, continues to cool and to grow secondary scale, both of which occurrences are detrimental to the economy of the process and quality of the product. Moreover, the more the slab cools down before it enters the roll bite, the higher the temperature to which it has tobe heated by the furnace and, of course, at higher temperatures the slab loses heat more rapidly both by radiation and by convection and it also develops more scale, thus making a vicious circle.

The disposition as per applicants invention, where the feeding force is reduced to one-fourth or even less than what is necessary in a straight mill as shown in abovementioned Patent No. 2,811,060, permits the location of the feeding mechanism considerably farther from the planetary mill because conditions that produce buckling are avoided. In this case applicant has conceived an idea to even further take advantage of this condition by dividing the heating operation of the slab into two steps. First, preheat the slab in a tunnel furnace disposed immediately ahead of the mill to about750 or 850 C. (more or less depending on certain materials and other considerations) and then place additional heating means along the slab after it has passed the feed roll and before it enters the planetary rolls. Such means are, for instance, propane and oxygen burners, or heating by electric resistance, either by contact or by induction, including high frequency induction. FIG. 4 shows the location of such induction coil 34 which can be split into two or more sections in order to accommodate guides 35 which would lead the end of the workpiece through the coil into the roll bite.

It will be clear to one skilled in the art that with steel slabs at such low preheating temperature as around 800 C., scaling and, therefore, the losses through scalingwill be very moderate. On the contrary the second stage of Cir heating up to forging temperature will be only slightly ahead of the planetary rolls, with the consequence that there will be less heat loss because there will be substantially no waiting period between heating and rolling, and, secondly, the time exposure to the high heat is relatively short and, therefore, the chances of scaling at this temperature are considerably reduced. Moreover, because of the compactness of this installation, it is perfectly easy to dispose a suitable hood around the slab and the secondary heating means to which a protective atmosphere can be circulated thus eliminating all oxidation.

Another factor should be considered in the relation to the heat loss to which the workpiece is subjected between the furnace exit and the beginning of the roll bite. Assuming that in a given straight line planetary mill the workpiece advances into the roll bite at, say 10 f.p.m., and the distance between the furnace exit and the beginning of the roll bite is 5 ft. then the workpiece will be exposed to the outside atmosphere for 30 seconds. But if, according with present application, the workpiece is fed into the roll bite at a given angle then the feeding speed will increase according to the ratio:

V cos a where V represents the width of the slab and V the width of the strip after reduction.

A feeding angle a of 60 will double the feeding speed and, therefore, the slab would be exposed to the atmosphere only for 15 seconds.

All the above disclosures were directed at a planetary mill where the work roll movement is in the direction of the movement of the workpiece. Obviously, the direction of the planetary mill can be reversed and that presents certain salient advantages as hereinafter described. However, the realization of such operation has encountered difficulties in straight line cyclic mills, chiefly because reverse rolling still further increases the demand for the feeding force which is already nearly critical when operating the mill in the forward direction. The present invention is, on the contrary, particularly adapted for moving the work rolls in the opposite direction to the movement of the workpiece primarily for the reason that the feed rolls can exert a feeding force upon the roll bite far beyond the capabilities of feed rolls in a straight planetary mill because of the friction effect by the side guide. As illustrated in FIG. 3 of Patent No. 2,710,550, the work rolls contact the unreduced portion of the slab first and progress toward the reduced portion. Due to the sudden impact of the work rolls against the slab surface, a wave or hump is formed on the unreduced portion of said surface, just ahead of the initial contact of the work roll. If the angle of the path of the work rolls at contact with the slab exceeds a certain critical bite angle (usually about 16 degrees), such hump grows into a continuous backfin as described in US. Patent No. 2,710,550, and as illustrated in FIGS. 10 and 11 of said patent. When rolling on a planetary mill with the planetary cages rotating in the same direction in which the slab is advancing into the roll bite, it is preferable that the formation of backfin be avoided because the rotation of the planetary cages tends to draw the backfin particles into the roll bite and spoil the surfacev of the product. For this reason straight rolling planetary mills must be dimensioned large enough so as to stay below the critical bite angle for the slab thickness they roll.

Referring now to FIG. 7, when the rotation of the planetary assemblies is reversed, so that the back up rolls 15 rotate against the direction in which the slab advances, a backfin 36 is formed almost irrespective of the critical bite angle, and because of the reverse rotation the backfin accumulation is expelled back and away from the roll bite by the action of the passing work rolls 12, rather than drawn into the roll bite, so that the danger of the backfin being rolled into the surface of the strip is eliminated. In this case backfin 36, or what amounts to scarfing of the slab surface layer, develops into a continuous or discontinuous formation at the beginning of the roll bite. The accumulated backfin can be wound in coils 37 or disposed of by any suitable means.

In reverse rolling, the angle of bite at the very entry of each roll in contact with the workpiece is more inclined against the rolling direction than in the forward rolling, so that an appreciably greater feeding force has to be applied. It should be clear, therefore, that the method of angular rolling as described herein, greatly facilitates reverse rolling because of the fact that the magnitude of the feeding force to be overcome by the feed rolls is substantially reduced as described above. Moreover, and for the same reason, it is possible to place the feed rolls at a certain distance away from the roll bite, without danger of buckling the slab. This renders the entry side of the mill more accessible so that an apparatus for removing or coiling the accumulated backfin can be installed close to the roll bite, without interfering with the rolling or the feeding operation.

A still more important advantage is that, since the critical point of backfin formation no longer applies in reverse rolling and the feeding force is reduced in angular rolling, a planetary mill of smaller diameter can be employed for a given slab thickness. For instance, for forward rolling the 7" thick x 50" wide slab mentioned in the first paragraph of the specification, a 126" diameter planetary mill would be required in order to stay below the critical bite angle. A mill of such size is beyond practicable manufacturing possibilities today. According to the present invention, a mill in angular reverse rolling only two-thirds of that size, that is, 84" in diameter, is perfectly adequate. A mill of such proportions is neither too large nor too expensive to build today.

As has been mentioned with reference to the above quoted Patent No. 2,710,550, the possibility of automatically, steadily and controllably removing the surface layer of the slab by means of a backfin is of appreciable interest to the art of rolling steel and alloyed steel strips. It is well known in the art that there are many defects present on the surface of the slab such as rolled-in inclusions, slivers, rolled-in scale, small surface cracks and many others, which, unless spotted and removed before the slab is rolled into a strip, will cause defective spots and rejects of the finished sheets. In the production of low carbon steel strips such as autobody sheets, this is usually accomplished by so-called scarfing of the slabs. One method is by burning the surface layer with a stream of oxygen. In the alloy steel field, this is a still more costly operation which involves grinding of the entire surface of the slab with heavy snubbing wheels. Since, if my method is used, scarfing can be integrally connected with the hot or cold cyclic rolling operation, there is substantially no extra cost involved in doing it, no labor charges and no extra operation.

Quality is also improved because scarfing is effected mechanically as a result of the division of the stream of the hot rolled metal under full rolling pressure, thereby excluding atmospheric oxygen. This means that surface cracks and other defects, even if not removed completely, will have a great chance of being completely welded and integrated into the sheet because of heavy elongation and plastic reduction under all-sided pressure and under the exclusion of oxidizing atmosphere.

Certain methods of producing slabs, especially continuous casting, do not lend themselves to frequent changes from one slab width to another. The present invention solves this problem also, since, out of one mould in a continuous casting machine, the planetary mill described herein can produce a wide range of widths by simply altering the angle of feeding of the slab.

Because the feeding force is reduced, a cyclic mill as per my invention can also function with a feeding appa- 1G ratus which engages only the edges of the slab which may be convenient in some cases.

In such a feeding apparatus, one or more pairs of lateral feed rolls are used. The lateral feed rolls contact the slab at its edges effecting a slight reduction of the slab, thereby imparting a uniform width to the workpiece. For this purpose, the feed rolls are mounted in such a way that the distance between them is adjustable, which enables them to accept workpieces of different widths, or to reduce a given workpiece to a required width. The contacting surface of the feed rolls is properly shaped so that they impart the proper curvature to the edges of the workpiece entering the roll bite.

FIGS. 8, 9, and 10, illustrate an arrangement of such rolling instrumentality, where the feed rolls 41 are disposed in such a way that they engage the workpiece at its edges. Feed rolls 41 are driven by spindles 42 through a gear arrangement 43. The distance between the feed rolls is governed by a screwdown arrangement, which may be effected as shown in FIG. 9 by locating shafts 44 of the feed rolls 41 in eccentric sleeves 45 which can be rotated by means of gears 46 on shafts 47. The rotation of eccentric sleeves 45 will alter the position of the feed roll shafts 44 varying, therefore, the distance between the rolls. This may be done by an adjusting shaft 48 having worm gears 49 thereon which drive the gears 46 by means of the shafts 47 through helical gears 51 mounted thereon.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efiiciently attained and, since certain changes may be made in carrying out the above methods and in the constructions set forth without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of producing strip material from a slab by plastic deformation in a cyclic mill having reducing rolls and a feeding instrumentality, comprising the steps of, feeding the slab into the reducing rolls in the plane of strip delivery from the cyclic mill but at an angle to the direction of strip delivery from the cyclic mill, applying a force against the edge of the slap as the slab enters the reducing rolls, said force not affecting the slab during and after the roll pass, and rolling the slab.

2. The method defined in clam 1 and further including the step of vibrating the thrust-absorbing member in synchronization with the action of the reducing rolls in such a manner that the thrust-absorbing member exerts a force on the slab having one component parallel to the direction of strip delivery from the mill and a second component in the direction of the feed of the slab whereby the crest of the thrust generated by the reducing rolls is countered by the crest of the thrust applied by the thrust-absorbing member.

3. The method of producing strip material from a slab by plastic deformation in a cyclic mill having reducing rolls and a feeding instrumentality, comprising the steps of:

(a) feeding the slab by means of the feeding instrumentality (i) into frictional contact, along one edge of the slab, with a thrust-absorbing member extending substantially parallel to the direction of feeding of the slab,

(ii) into frictional contact with a second thrustabsorbing member disposed proximate to the reducing roll at least in the forward portion of the 1 1 zone of plastic deformation and extending substantially parallel to the direction of strip delivery from the mill, and (iii) into the reducing rolls in the plane of strip delivery from the mill but at an angle to the direction of strip delivery from the mill, and

(b) rolling the slab, whereby each of the thrust-absorbing members generate reactive forces perpendicular to the plane of contact between the slab and the respective thrust-absorbing mem bers to counterbalance the effects of asymmetric support of the slab in the zone of plastic deformation and to partly relieve the feeding instrumentality of the thrust generated by each successive pair of the reducing rolls.

4. The method defined in claim 3 and further including the step of adjusting the angle of the plane of contact between the second thrust-absorbing member and the slab to the optimum rolling conditions.

5. The method defined in claim 3 and further including the step of vibrating the thrust-absorbing member in synchronization and in phase with the cyclic contact of the reducing rolls with the slab to further relieve the feeding instrumentality of the thrust generated by the reducing rolls.

6. The method of producing strip material from a slab by plastic deformation and simultaneously scarfing the slab in a planetary cyclic mill having planetary reducing rolls, back-up rolls and a feeding instrumentality, comprising the steps of:

(a) feeding the slab by means of the feeding instrumentality into the reducing rolls in the plane of strip delivery from the mill but at an angle to the direction of strip delivery from the mill,

(b) guiding one side of the slab as it enters the reducing rolls by means of a thrust-absorbing member taking up the thrust generated by the reducing rolls,

(c) rotating the back-up rolls in a direction opposite to the direction of strip delivery from the mill, and

(d) rolling the slab, whereby the feeding instrumentality is partly relieved of the thrust generated by the reducing rolls.

7. Apparatus for rolling strip material from a slab by plastic deformation thereof comprising, a cyclic mill having reducing rolls and feeding rolls, said feeding rolls positioned with relation to said reducing rolls to feed the slab in the plane of strip delivery from the cyclic mill and at an angle to the direction of strip delivery from the cyclic mill, and a thrust-absorbing member positioned on the input side of the mill between said feeding rolls and said reducing rolls and positioned to contact the slab along one edge thereof adjacent the zone of deformation to absorb a portion of the force exerted on the slab by the reducing rolls.

8. The structure defined in claim 7 and further including a second thrust-absorbing member extending from the first thrust-absorbing member and disposed at an angle thereto, said second thrust-absorbing member extending toward said reducing rolls in the zone ofplastic deformation to support one edge of the slab in the zone of plastic deformation to thereby reduce the consequences of asymmetric support of the edges of the slab.

9. The structure defined in claim 8 wherein said second thrust-absorbing member is angularly adjustable with rela tion to the first thrust-absorbing member.

10. The structure defined in claim 9 wherein said second thrust-absorbing member is provided with a convex face adapted to engage the edge of the slab.

11. The structure defined in claim 7 wherein the face of said thrust-absorbing member is provided with a plurality of saw-tooth serrations whose pitch is fixed with relation to the feed of said slab, the pitch of said serrations being so selected that minimal resistance is offered to the slab in the direction of feeding but appreciable friction is offered to the slab in a direction opposite to the direction of feeding.

References Cited by the Examiner UNITED STATES PATENTS 2,345,765 4/44 Michel 35.1 2,505,146 4/50 Ryan.

2,787,046 4/57 Wagstaff 29-18 2,995,050 8/61 Karron et al 8043 WILLIAM J. STEPHENSON, Primary Examiner.

LEON PEAR, Examiner. 

7. APPARATUS FOR ROLLING STRIP MATERIAL FROM A SLAB BY PLASTIC DEFORMATION THEREOF COMPRISING, A CYLIC MILL HAVING REDUCING ROLLS AND FEEDING ROLLS, SAID FEEDING ROLLS POSITIONED WITH RELATION TO SAID REDUCING ROLLS TO FEED THE SLAB IN THE PLANE OF STRIP DELIVERY FROM THE CYCLIC MILL AND AT AN ANGLE TO THE DIRECTION OF STRIP DELIVERY FROM THE CYCLIC MILL, AND A THRUST-ABSORBING MEMBER POSITIONED ON THE INPUT SIDE OF THE MILL BETWEEN SAID FEEDING ROLLS AND SAID REDUCING ROLLS AND POSITIONED TO CONTACT THE SLAB ALONG ONE EDGE THEREOF DJACENT THE ZONE OF DEFORMATION TO ABSORB A PORTION OF THE FORCE EXERTED ON THE SLAB BY THE REDUCING ROLLS. 